1. Field of the Invention
The present invention relates in general to computer networks. More specifically, the present invention relates to a method and a system for address management of mobile nodes in computer networks.
2. Description of Related Art
The Internet Protocol (“IP”) is an addressing protocol designed to route traffic within a network or between networks. In IP, nodes, which may be either hosts or routers, are typically identified by a unique network address, an “IP address.” Most widely used versions of IP, such as IP version 4 (“Ipv4”), assume that a node's IP address uniquely identifies the node's point of network attachment. As a result, if a node changes its point of attachment without changing its IP address, it will normally lose its ability to communicate using IP.
With the explosive growth in the use of mobile computers, such as notebook computers and personal digital assistants (PDAs), for accessing the Internet, this limitation is becoming increasing unacceptable. In response, various forms of “mobile IP” have been suggested. Mobile IP typically allows a mobile node to dynamically change its network connectivity in a manner that is transparent to the user.
One such form of mobile IP is described in C. Perkins, “IP Mobility Support,” RFC 2002, October 1996, which is incorporated herein by reference. In this form of mobile IP, each mobile node maintains an IP address, its “home address,” that is part of its home network's domain, and the mobile node uses its home address whether it is connected to its home network or to a foreign network. However, with the rapid increase in the use of the Internet, the number of available IP addresses using the 32-bit address field provided for by Ipv4 is becoming very limited. With each mobile node assigned its own IP address as well, the problem of limited address space is made even more acute.
Various approaches for dealing with the problem of limited IP address space have been proposed. IP version 6 (“Ipv6”) proposes the use of a 128-bit address field for IP addresses. However, a large number of legacy networks and nodes are likely to be limited to 32-bit IP addresses for many years to come.
Network address translation (“NAT”) has also been proposed as at least a temporary solution. In the NAT approach, a node uses a private address for communication on its local network, and a NAT device translates this private network is translated to a global IP address for communication with an external network. However, the NAT approach has a number of disadvantages, namely, it tends to be computationally expensive, can cause security problems by preventing the use of certain types of encryption, and can prevent the use of certain applications that do not support NAT.
Accordingly, it is desirable to provide an improved approach for mobile IP that accommodates the limited availability of IP addresses in Ipv4 in a computationally efficient manner.